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Artificial kidney definition:

Any mechanism that assists or performs the job of human kidneys is an artificial kidney. 

Artificial kidneys are a part of renal replacement therapy and can be of more than one type.

Artificial kidney classification

Artificial kidneys can be classified as follows:

  1.     Hemodialysis
  2.     Hemofiltration
  3.     Hemodiafiltration
  4.     Bioengineered/bioartificial kidney

Although artificial kidney classification can consist of all of the above, the term is used most often to refer to hemodialysis.

Hemodialysis

Definition: Hemodialysis is the process of blood purification by means of an artificial kidney of a person whose kidneys are not working. It involves passing the blood through extracorporeal mechanisms.

When kidneys are able to perform only 10 to 15% of their regular function of water removal from the body, hemodialysis is recommended by doctors.

Mechanism

Hemodialysis works in the following way

  •       The doctor makes an access or entrance in the patient’s body through which blood is supplied to the dialysis machine.
  •       For this purpose, a minor surgery to the arm is usually done.
  •       The dialysis machine has an artificial filter or more accurately, an artificial kidney called the dialyser.
  •       The artificial kidney or the dialyser has two parts one where the blood goes and one which contains the purifying fluid or the dialysate.
  •       These two parts are separated by a very thin membrane.
  •       This thin membrane does not allow big particles such as blood cells, proteins and other essential components to pass through.
  •       However, small particles solutes like potassium, urea, creatinine and extra fluid pass through. Thus, blood is purified.

Need for hemodialysis:

Kidneys remove waste from the body and also manufacture substances needed by the body. In the absence of this filtration, toxic materials accumulate inside the body and cause damage to our health. In such an instance, a person may experience such symptoms as nausea, water retention, vomiting and fatigue. Hemodialysis performs some functions of a human kidney.

Where can hemodialysis be done?

Hemodialysis can be done

  1.     At home
  2.     In a hospital
  3.     At a dialysis center.

Length of treatment

The length of a dialysis session depends on the frequency with which it is performed. For example: 

  •       In a dialysis center, dialysis is conducted three times a week, lasting for 4 hours each.
  •       At home, 4 to 7 times a week, lasting for short amounts of time.

Dietary restrictions

Patients are advised to have a diet low in phosphorus, sodium, potassium and fluids and high in proteins.

Disadvantages

  •       Patients on dialysis are restricted from travel because of the frequent need for the dialysis sessions.
  •       Dialysis machines are a relatively advanced technology not available to all.
  •       Water quality needs to be carefully monitored, and the electricity supply needs to be very reliable.
  •       The caregivers need to be well versed with the technology.
  •       This is an expensive procedure, and not everyone can afford it.

Types of hemodialysis

  1.     Conventional hemodialysis: This is done three times a week for 4 hours.
  2.     Daily hemodialysis: Usually done by patients at home. The sessions are shorter.
  3.     Nocturnal hemodialysis: Performed at night for 3 to 6 hours while the patient sleeps.

Hemofiltration

Another form of artificial kidney is hemofiltration. This treatment is usually given to people who suffer from acute kidney injury (AKI). People suffering from multiple organ dysfunction may also benefit from hemofiltration. It involves:

  1.     Purification through a semipermeable membrane, like in the case of hemodialysis.
  2.     However, unlike hemodialysis, hemofiltration does not use a dialysate.
  3.     The movement of solutes is governed through convection and not diffusion.
  4.     A hydrostatic pressure of positive charge pushes the solutes from the blood to the filtrate compartment.
  5.     This is an advantage over hemodialysis because the hydrostatic pressure pushes small and large solutes at a similar rate through the filter membrane.

Disadvantages

Hemofiltration has similar disadvantages as hemodialysis. People on this treatment need to

  1.     Restrict their travel.
  2.     Be financially sound in order to afford this treatment.
  3.     Have access to a high-quality water supply.
  4.     Have access to a constant electricity supply.
  5.     Live in a place that has access to this technology.
  6.     Have a carefully monitored diet.

Hemodiafiltration 

Sometimes hemodialysis is used in conjunction with hemofiltration. This is called hemodiafiltration. It follows the following procedure:

  •       The blood compartment received the blood.
  •       The solutes are moved at a high rate into the filtrate compartment.
  •       This happens because a high rate of ultrafiltration is used in hemodiafiltration.
  •       The substitution fluid used to replace the water and solutes is infused directly into the blood.

This combination of the two procedures resulting in hemodiafiltration is theoretically effective since the high rate of ultrafiltration is efficient in removing both big and small solutes.

Disadvantages

Like the previous two procedures, hemodiafiltration too has similar disadvantages. This is a highly technical and delicate procedure and requires careful and skilful administration by the caretakers. It combines the drawbacks of both the previous procedures.

Artificial kidney examples

With the advancements in technology, a vast amount of research is being conducted to improve the efficiency of treatment from an artificial kidney. Some of these include an implantable artificial kidney, a wearable artificial kidney and implantable renal assist device.

Implantable artificial kidney

This is an under progress project.  Develop an artificial kidney which is a bio-hybrid device capable of imitating a healthy kidney.

The project aims to develop a device that can remove enough waste from the body so that the patient does not need dialysis. 

The developers of the project are working with silicon nanotechnology and porous microchips. Each pore of the microchip aims to perform a specific task or function involved in the general functioning of filtering.

The project is working on ways to keep the device secure from the body’s immune response, which might reject it. If they are successful, the developers want the device to be small enough to fit inside the body of a patient.

Wearable artificial kidney

A wearable artificial kidney is a dialysis machine that can be worn by a person. This is another project researchers are working on.

The result, aimed at developing a wearable artificial kidney, is to provide patients suffering from end-stage kidney disease with a portable machine that performs the functions of a kidney.

Human kidneys work 24 hours a day, seven days a week. This means a healthy person’s kidneys work 168 hours a week. But a person who is on dialysis receives only about 12 hours of blood filtration in a week. This results in the deterioration of quality of life.

There is a prototype of a wearable artificial kidney. It is 

  •       Approximately 10 pounds
  •       Powered by a 9-volt battery
  •       Designed to run continuously
  •       Designed to use less than 500ml of dialysate.
  •       Able to show patients a certain amount of freedom in movement.

Conclusion

In India, the first hemodialysis was performed in an erstwhile royal family member in CMC Vellore(medical college) , Tamil Nadu. For many years the technology of hemodialysis was restricted to 4 places in India. But this number has improved manifold since then. There were about 12,881 hemodialysis centers distributed all over the country in an estimate from 2018.

However, like most secondary and tertiary healthcare, dialysis is also mostly provided by the private sector. Since this technology is still quite expensive, there is plenty of room for